1. Field of the Invention
The present invention relates to a demagnetizer for display unit suitably applied to a TV receiver and TV monitor, etc.
2. Description of the Related Art
A shadow mask or aperture grille for selecting colors is provided within a color cathode-ray tube of a TV receiver and TV monitor for example and a thin steel plate is used for that. Due to that, when the TV receiver or TV monitor is carried over by airplane or the like to use at a remote place distant from the manufacturing site thereof, the shadow mask and the like is often magnetized by an external magnetic field such as terrestrial magnetism. Then an orbit of electron beam is disturbed around the shadow mask in the tube, hence degrading its color purity. In order to prevent such problem, such a demagnetizer as shown in FIG. 12 is incorporated in the TV receiver or TV monitor. By the way, although the following explanation will be made exemplifying the shadow mask, the same applies to the aperture grille as well.
A degauss coil 1 is attached to the shadow mask of the TV monitor, for example, in the demagnetizer shown in FIG. 12. When a power switch 2 of the TV monitor is turned on, a demagnetizing current I which attenuates in accordance with the lapse of time is flown in the degauss coil 1 via a thermistor 3 of positive characteristic. Thereby, a flux density generated from the degauss coil 1 is converged to the origin and the residual magnetism on the shadow mask is removed (as described in U.S. Pat. No. 5,148,083 for example).